<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* #wrap{
      background-color: red;
    } */
        /* .box{
      width: 200px;
      height: 200px;
      background-color: pink;
    }
    div {
      background-color: blue;
    } */

        /* .box div{
      background-color: aquamarine;
    } */

        /* #one{
      width: 100px;
      height: 100px;
      background-color: red;
    } */

        /* .box div{
      background-color: rgb(239, 57, 11);
    }
    .box > div{
      background-color: aquamarine;
    } */

        /* .box > .two{
      background-color: blueviolet;
    } */
        /* .one + .two {
      width: 100px;
      height: 100px;
      background-color: red;
    }
    #two{
      background-color: blueviolet;
    }
    .one, .two{
      background-color: chartreuse;
    } */


        /* .box .input{
      background-color: red;
    }
    .input[type="text"]{
      background-color: blueviolet;
    } */

        /* .input:nth-child(1){
      background-color: red;
    } */

        .one::after {
            content: "123";
            display: block;
            width: 20px;
            height: 20px;
            background-color: rgb(38, 63, 226);
        }

        .one:hover {
            background-color: red;
        }
    </style>
</head>

<body>
    <div class="box" id="wrap">
        <!-- 
    <div class="one">1</div>
    <div class="two" id="two">2</div>
    <div class="two">2</div>
    <div class="two">2</div> -->
        <!-- <input type="text" class="input" id="input" value="hello">
    <input type="text" class="input"> -->

        <div class="one"></div>
    </div>
</body>

</html>